1. Field of the Invention
The present invention relates to a speed reduction device having an overrunning clutch and, particularly, a vehicular rotary machine which has a starting motor or a starter-generator.
2. Description of the Related Art
A common starter motor for a vehicle has an overrunning clutch disposed between the pinion shaft and the driving shaft of the motor to prevent over-run of the starter motor when an engine starts and the starter motor is driven by the engine. A speed reduction device is sometimes employed in the starter motor to reduce the size of the starter motor and also to increase the engine starting torque. For this purpose, an eccentric-gear speed-reduction device, which is composed of a drive shaft having an eccentric ring and an internal gear in mesh with the eccentric gear and provides a large speed reduction ratio has been proposed.
The above-described starter motor, however, needs a complicated structure to combine a shaft, bearings, the starter motor, the overrunning clutch and the speed reduction device, resulting in a bulky rotary machine.